The Boston marathon bombing may not represent the work of al-Qaida, but still could be a harbinger of future attacks targeting Americans in their own country, warns Gen. Michael Hayden, the retired four-star general and past director of both the National Security Agency and the CIA.

In an exclusive interview, Hayden told Newsmax that the attack may be an act of domestic terrorism, or could be the act of an al-Qaida inspired, lone wolf. Either of those scenarios would account for the fact that al-Qaida and its affiliates have yet to claim credit for the two bombs that went off almost simultaneously near the finish line of the Boston Marathon on Monday.

But he said the bombing could foreshadow future attacks on the U.S. homeland, even if al-Qaida was not involved.

“As we move into this next phase of this war with al-Qaida,” said Hayden, “and their ability to conduct massive-casualty attacks against iconic targets of the spirit of 9/11, these are probably the kinds of attacks that they would then resort to, in order to try to achieve their objectives.”

Among the hallmarks of this new era of terrorism, he said, is that the attacks “are not overly complex, or at least not complex in the way that it requires a massive cell of people to be involved.”

Hayden said the ultimate evaluation of the level of sophisticated involved in the bombing will “come down to the weapon, how complex that was, how reliable it was, and whether the reports were true that there were other weapons out there as well.”

The former CIA chief said he has long feared that more numerous, less sophisticated attacks against the United States may be inevitable.

“This regrettably, if it does turn out to be al-Qaida based terrorism, might be the new normal,” said the intelligence expert who led the U.S. intelligence apparatus under former President George W. Bush. “I’ve been fond of saying that because of all the things that we’ve done well since 9/11, future attacks against the United States will be less complex, less likely to succeed, less lethal if they do succeed — but they’re just going to be more numerous.

“And this may just be an example of one of those more numerous, less complex attacks succeeding,” he said, quickly adding, “But we don’t know that yet . . . we’ve just got to let the facts take us where they will.”

Asked to comment on the response that led FAA officials to close Boston airspace, and to tighten security in New York and Washington, Hayden said this too was a sign of the times.

“Sadly, we’re getting really good at this,” he told Newsmax. “We’re getting really good at this because — it’s sad — we all realize that this is now the kind of the world we live in. The first responders knew what to do the instant of the detonation in Boston, and then we had these ‘sympathetic alerts,’ I think we’d call them in the military, in other cities just as a precaution, not based as far as I can tell on any kind of threat intelligence. But these systems are ready to go.”

Overall, Hayden said, America remains a “tough target” for terrorists to attack. “We’re a tough target because we’re aggressive against our enemies abroad, we take the fight to them,” he said. “We’re a tough target because Americans have learned to live with a great deal of inconvenience. And we’re a tough target because Americans are a pretty resilient people.”

Hayden predicted that security officials in the United States and abroad will step up their security efforts in the days to come.

“You always fear a copy-cat attack,” Hayden told Newsmax. “If someone has gotten away with something in one location, others equally inspired will view that as a methodology they can use as well.

“We looked at the attack in Mumbai [India] shortly before Thanksgiving in 2008, and shook our heads in worry that others would go to school on that attack. To date, that hasn’t happened. But that doesn’t mean it won’t happen in this case.”

Asked how Americans should respond, knowing that terrorist mayhem has come to America’s shores, Hayden replied: “The best of all possible worlds is sort of a blend of the British bumper sticker and the American one. The British one is, ‘Keep calm and carry on.’ The American is, ‘If you see something, say something.’

“You just put those two together,” said Hayden, “and move on with your life.”